Device and Method for Atraumatic and Percutaneous Formation of an Arteriovenous Fistula

ABSTRACT

Provided herein are novel devices for the formation of arteriovenous fistulas, which may aid subjects in need of hemodialysis. The novel devices are provided in a non-surgical procedure, greatly decreasing the cost and increasing the convenience of placing an arteriovenous fistula. The devices are atraumatic, and consist of a sutureless anastomosis device and conduit. Methods and tools for placing the devices in vivo are disclosed, including a magnetic-assisted method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication Ser. No. 62/521,920 entitled “Device and Method forAtraumatic and Percutaneous Formation of an Arteriovenous Fistula,”filed Jun. 19, 2017, the contents which are hereby incorporated byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

Millions of people worldwide suffer from end-stage renal disease orother conditions requiring hemodialysis treatment. Hemodialysis requiresaccessing the circulatory system for the withdrawal, cleansing, andreturn of the patient's blood. Methods of accessing the patient'scirculatory system include tunneled catheters, arteriovenous grafts, andarteriovenous fistulas (AVFs). The type of circulatory access used inhemodialysis has important consequences for the patient. Of thesemethods, it is widely accepted that AVFs have the best outcomes, withthe lowest risk of morbidity and mortality for the patient. AVFs areless prone to infection and are more durable than both tunneledcatheters and arteriovenous grafts. However, the current method ofplacing an AVF is a surgical procedure, requiring the services of highlytrained personnel (e.g. surgeons, anesthesiologists, etc.) and the useof associated operating room equipment. Such resources are expensive andin short supply in some communities, creating practical, economic, andmedical barriers to AVF placement. As a result, less than 30% ofpatients in the United States initiate hemodialysis with AVFs, with themajority using inferior tunneled catheter access.

Accordingly, there is a need in the art for devices and procedures thatsimplify AVF formation. Various methods of creating percutaneous AVF'shave been developed. A first set of AVF technologies includesdevice-based methods of forming AVFs, encompassing various implants andsurgical methods. Exemplary systems are described in: PCT InternationalPatent Application Publication Number WO201392208, entitled “Stent toAssist in Arteriovenous Fistula Formation,” by Florescu; United StatesPatent Application Publication Number 20110054492, entitled “MedicalDevice for Repairing a Fistula,” by Clark; and U.S. Pat. No. 7,691,140,entitled “Anstomosis device for vascular access,” by Bates et al. Themajority of these mechanical AVF solutions employ barbs, hooks, andother features that increase trauma to the treated area, and none ofthese prior art methods or devices have been widely adopted.

A second type of AVF technology is tissue welding, encompassing fusionof tissues using thermal, electrical, RF, or laser energy. Exemplarytissue welding systems include the EVERLINQ™ system (TVA MedicalSystems, Austin, Tex., USA); systems described in U.S. Pat. No.9,017,323, entitled “Devices and Methods of Forming a Fistula,” byMiller et al.; and the ELLIPSYS™ system (Avenu Medical, San JuanCapistrano, Calif., USA). However, tissue welding technologies haverisks associated with off-target thermal injury, resulting in nerveinjury, pain, necrosis and other complications. Furthermore, some tissuewelding systems create a fistula without providing any means to directblood flow into the superficial venous system, resulting in the need fora second endovascular or surgical procedure to create a functional AVF.

Accordingly, there remains a need in the art for novel AVF methodologiesthat are clinically practical, cost effective, and which avoid the sideeffects and potential need for additional interventions associated withtissue welding.

SUMMARY OF THE INVENTION

Provided herein are novel devices and methods for the percutaneousformation of AVFs. The novel inventions disclosed herein enable theefficient and economical placement of fistulas such as AVFs. The systemsdescribed herein encompass novel devices, novel methods, and variousimprovements to the art. In one aspect, the scope of the inventionencompasses the novel deployment of atraumatic anastomosis devices inthe context of fistula formation. In one aspect, the scope of theinvention encompasses the novel use of a fistula implant comprising aconduit for creating optimized blood flows at the fistula site. In oneaspect, the scope of the invention encompasses novel nonsurgical methodsof forming fistulas. In one aspect, the scope of the inventionencompasses novel placement methods that enable inexpensive and facilefistula creation.

The methods of the invention advantageously allow the placement of theimplant and formation of an AVF in a minimally invasive, atraumatic,endovascular procedure. This allows placement in a clinical venue,rather than surgical setting, without need for subspecialty care such asanesthesia or surgical staff. This greatly reduces the practical andeconomic barriers to the installation of an AVF, as compared to currentsurgical methods required for AVF installation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C. FIG. 1A depicts the vascular system of the arm.Site 102 is a potential target area for formation of an AVF between thevenous perforator branch in the antecubital fossa and the distalbrachial artery 103, or between the venous perforator branch in theantecubital fossa and either the proximal radial or proximal ulnarartery, just beyond the brachial artery bifurcation. Site 101 is apotential introduction site for introducing the crossing device.Potential introduction sites for introducing the complementary placementdevice are in the radial artery 105 or ulnar artery 104. FIGS. 1B and 1Cdepict surgical AVF sites and connections.

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, and 2I. FIGS. 2A, 2B, 2C, 2D, 2E,2F, 2G, 2H, and 2I depict an exemplary implementation of the inventionwherein the implant of the invention is deployed to connect a first anda second blood vessel by use of a crossing device and complementaryplacement device. 2A: The crossing device 201 is advanced through thefirst blood vessel 203 to the target site. Next, the complementaryplacement device 215 is advanced through the second vessel 205 to thetarget site. 2B: the magnetized tip 202 of the crossing device 201attracts the magnetized tip 208 of the complementary placement device215 with sufficient force to pull the wall 204 of the first vessel intoproximity with the wall 206 of the second vessel. 2C: Cutting element209 is deployed from the tip 202 of the crossing device, piercing thefirst and second vessel walls (204 and 206) and entering a hollowinterior portion 207 of the complementary placement device 215. Thecutting element may be retracted or remain in the hollow interior of theplacement device. 2D: A guide wire 201 is extended from the tip 202 ofthe crossing device 201 and extended into the hollow cavity channel 207of the placement device in the second vessel 205. 2E: The tip 202 of thecrossing device 201 is extended into the second vessel 205 by theopening created by the cutting tool. 2F: The implant is partiallyejected such that the first set of hands 211 is deployed from the tip202 of the crossing device, inside vessel 205. 2G: The crossing deviceis withdrawn such that the tip 202 is pulled back into the first vessel203. The first set of hands catches and pulls the wall 206 of the secondvessel snugly against the wall 204 of the first vessel. 2H: The implantis further ejected from the tip 202 of the crossing device 201 such thatthe second set of hands 212 of the implant is ejected from and aredeployed such that the wall 204 of the first vessel and the wall 206 ofthe second vessel are sandwiched between the first set of hands 211 andthe second set of hands 212. 2I: The crossing device 201 is withdrawn,releasing the conduit 212 of the implant from the crossing device andleaving it in place in the first vessel 203, with a fistula createdbetween vessels 203 and 205 created by the central annular section ofthe implant (not visible in this view).

FIGS. 3A, 3B, 3C, 3D and 3E. FIGS. 3A, 3B, 3C, 3D, and 3E depict variouselements of the implant of the invention. FIG. 3A depicts a section ofan exemplary sutureless anastomosis device comprising a piece of nitinolwire bent to create a bottom row of hands 301 and a top row of hands302. As depicted here in the relaxed configuration, the hands aresubstantially perpendicular to the longitudinal axis of the implant andthe row of hands 301 and 302 form two parallel flanges. FIG. 3B depictsa top view of the sutureless anastomosis device comprising a hollowcentral portion 303. FIG. 3C depicts a side view of the entire implant,including the bottom hands 301 and top hands 302, connected to conduit305. The conduit comprises a scaffolding 305. FIG. 3D is a perspectiveview of the implant, making visible the hollow inner lumen portion 306of the conduit. FIG. 3E depicts the hands in the deflected, tensionedposition as they would be when stored in the implant housing of thecrossing device, with the hands deflected from their resting positionaround the annular structure 307.

FIGS. 4A, 4B, 4C, 4D, and 4E. FIGS. 4A, 4B, 4C, 4D, and 4E depict anexemplary process for placing the implant by use of a crossing devicewithout the aid of a complementary placement device to create an AVFbetween the venous perforator branch and brachial artery. FIG. 4Adepicts a cutting element 402 and guide wire 403 extended from thedistal tip 404 of the crossing device 401 across the vein wall into theadjacent artery. FIG. 4B depicts a first set of hands 405 deployed fromthe tip of the crossing device. FIG. 4C depicts the tip of the implantbeing withdrawn back into the vein with the hands pulling the arterywall. FIG. 4D depicts the second set of hands 406 of the distal portionof the implant (inset) being deployed to sandwich the vein and arterywalls together. FIG. 4E depicts the crossing device having beenwithdrawn, deploying the conduit portion of the implant in the vein.Blood flowing through the fistula is directed to the peripheral venoussystem 410, bypassing the deep venous system region 411 at which thefistula is formed.

DETAILED DESCRIPTION OF THE INVENTION

Various elements of the invention are described herein as having a“proximal” and a “distal” end. “Distal” and “proximal,” as used herein,are defined with respect to the operator (i.e., the medical person orpersons that are implanting the device in the patient). Accordingly, theproximal end is that end that is closest to the operator and theopposite, distal end is that end which is inserted first and furthestinto the patient.

Various parameters are described herein as being “within the range” oftwo numbers. Such reference will encompass the stated values and allvalues intermediate thereto. For example, if a parameter is stated to bein the range of 2-3 units, this will encompass all values greater thanor equal to two and less than or equal to three.

The various elements of the invention are described next.

Arteriovenous Fistula.

The various inventions disclosed herein are directed to methods offorming a fistula, i.e., a connection between any two two blood vesselsthat enables blood flow between them. The inventions are especially wellsuited to the formation of arteriovenous fistulas (AVFs), i.e. aconnection between an artery and a vein.

The AVFs of the invention may be formed in any part of the body. In apreferred implementation, the AVFs of the invention are formed in theupper arm at a point where the venous perforator branch in theantecubital fossa, which connects the superficial venous system to thebrachial veins, is in close proximity to the distal brachial artery orproximal radial or ulnar artery, just beyond the brachial arterybifurcation. The proximity of these blood vessels to each other createsan anatomic opportunity for minimally invasive creation of AVFs.Accordingly, the description provided herein will be made with referenceto creation of AVFs at this site. However, it will be understood by oneof skill in the art that the devices and method of the invention may beapplied and adapted to other regions of the body, including the lowerextremities, wherein it is practical to connect veins and arteries.

AVF Implant.

In one aspect, the scope of the invention encompasses a novelimplantable device for creating an AVF. An exemplary embodiment of thedevice is illustrated in FIGS. 3C and 3D. The implantable device will bereferred to herein as the “implant”. The distal end of the device isthat end of the tubular body which forms the anastomosis between thevein and artery. Proximal to this anastomosis-forming component andconnected thereto, the implant comprises a conduit component. In an AVFtype fistula, the conduit is placed the venous blood vessel of thefistula and directs the outflow of blood from the arterial vessel intothe vein. The novel conduit component confers several advantages. Theconduit acts as a bypass to direct outflow of blood from the arterialvessel away from the site of the fistula. When the AVF is formed in alocation that has a perforator branch connecting the superficial venoussystem to the venous system, for example, wherein the first blood vesselis the median cubital perforator, connecting to either the medialcubital vein, cephalic vein or basilic vein of the arm and the secondblood vessel is the brachial artery at its terminus (or the proximalradial or proximal ulnar arteries), the conduit can be placed such thatit directs blood flow away from the deep system to the superficialsystem, creating a favorable state of flow. This avoids the need forsecondary interventions such as embolization, speeds maturation of thetarget vein and results in quicker time to first cannulation.

The conduit component is a substantially tubular body having an outerdiameter, at its widest point, of about 100-150% of the diameter oflumen of the vein in which it will be placed, with dimensions thatensure snug fit against the vessel wall. Exemplary diameters of theconduit component are in the range of 2-9 mm, for example, in the rangeof 2-3 mm, in the range of 3-4 mm, in the range of 4-5 mm, in the rangeof 5-6 mm, in the range of 7-8 mm, in the range of 8-9 mm. The tubularbody may be tapered at its distal end, for example as depicted in FIG.3D, with a diameter, for example, in the range of 1-6 mm at its narrow,distal end, for example, in the range of 1-2 mm, in the range of 2-3 mm,in the range of 3-4 mm, in the range of 4-5 mm, in the range of 5-6 mm,or in excess of 6 mm. The taper provides for a smoother blood flow pathinto the vein, for example, the antecubital vein, and avoids turbulentblood flow that can cause complications such as clotting. The length ofthe conduit body may be in the range of 5-35 mm. In variousimplementations, the, the length of the conduit is in the range of 5-8mm, in the range of 8-10 mm, in the range of 10-12 mm, in the range of12-15 mm, in the range of 15-18 mm, in the range of 18-20 mm, or inexcess of 20 mm. In a preferred implementation, the length of theconduit is at least 15 mm to ensure that blood flowing from the arteryinto the cubital vein will bypass the deep venous system, increasingflow into the superficial cephalic vein.

The composition and configuration of the conduit component may vary. Inone embodiment, the conduit component comprises a metal scaffolding,covered by or embedded within a fabric or film of biocompatiblematerial. The metal scaffolding may comprise any metal lattice design,such as that found in stents, as known in the art. For example, thescaffolding may comprise a wire frame made up of interconnected,substantially parallel rows of interwoven metallic wires or likeelements, for example, in an undulating “zig-zag” or wave pattern,forming a lattice or cage-like structure. In one embodiment, the peaksof the zig-zag pattern are aligned in the longitudinal axis. In anotherembodiment, the lattice is a mesh, for example, a mesh comprising twosets of multiple, parallel rows of wire meeting at a right angle(creating square spaces between wires) or off-axis (creating trapezoidalspaces between wires). In another embodiment, the scaffolding maycomprise one or more spiral elements (e.g., parallel or crossingelements) which encircle the conduit from its distal to its proximalends.

The thickness of the wire may be any thickness that creates the desiredrigidity of the conduit portion. For example, wires of thickness of 0.1to (12 mm microns may be used.

The metal may comprise stainless steel, nitinol, cobalt chromium orother biocompatible metals known in the art, or a combination of theabove. In an alternative embodiment, the scaffolding comprises anelastic polymeric material rather than metal.

The scaffolding of the conduit may be manufactured by a suitable meansknown in the art. For example, in the case of metal scaffolding, thestructure may be manufactured by laser cutting of a metal tube using afinely controlled and focused laser beam and rotation of the workingsurface, as known in the art. Metal thickness in the range of 0.1-0.2 mmmay be used.

The covering may comprise polytetrafluoroethylene (PTFE), or othermaterials, such as synthetic polyester terephthalate textile forexample, materials used in covered stents. The covering may comprisefibrous materials in a woven or braided fabric, or may comprise a film.The covering may be porous. This use of PTFE or other prostheticmaterial covering the metal scaffolding aids in preventingpseudoaneurysm formation during percutaneous access creation.

The covering may cover the scaffolding, for example being wrapped orspooled around the scaffolding. For example, in one embodiment, thescaffolding is encapsulated between two sheets of covering material,such as PTFE. Alternatively, the scaffolding may be integral to thecovering, being made by dipping, spraying, or otherwise coating thescaffolding with the covering material. In one embodiment scaffolding isplaced over a form which defines the tapered inner lumen of the conduit,over which the scaffolding is placed prior to dipping, coating, orotherwise applying the covering.

The conduit will preferably be partially rigid, being rigid enough inthe radial axis to hold the shape of the lumen and maintain blood flow,with some degree of give to avoid tissue injury. In the longitudinalaxis, the conduit may be sufficiently flexible to bend with movement ofthe subject in which it is implanted. In one embodiment, the flexibilityof the conduit is consistent across the length of the structure. In oneembodiment, the rigidity of the conduit is variable across the length ofthe structure. Rigidity, in general or locally, may be tuned by thedesign of the scaffolding and/or covering material, for example, byvarying the thickness of the wires, the spacing between rows of wires,the frequency and size of elements interconnecting the rows, thethickness of the covering layer, etc.

In one embodiment, the conduit is coated with one or more agents. Forexample, the conduit may be coated with antibiotics, blood thinners,anti-inflammatory compounds, anti-proliferative compounds,pro-maturation compounds or other agents that facilitate healing,durability or prevention of infection.

The distal end of the implant comprises a sutureless anastomosis device.The sutureless anastomosis device comprises any device that can form ananastomosis without the requirement for sutures. Generally, oncedeployed in situ, the sutureless anastomosis device will comprise a ringstructure capped by two parallel flanges, wherein the arterial andvenous walls of the AVF are sandwiched together between the flanges,wherein the central aperture of the ring creates a fluid connectionbetween the adjoined artery and vein.

In an exemplary embodiment, as depicted in FIGS. 3C and 3D, thesutureless anastomosis device comprises the following basic elements: anannular body; a first set of deployable hands, a second set ofdeployable hands. The annular body comprises a ring, for example, a ringmade of wire elements, for example as depicted in FIGS. 3A and 3B. Inthe transverse dimension, the annular body defines a central hole oropening having a diameter, as in 303 of FIG. 3B. The inner diameter ofthe annular body defines the opening of the AVF when placed in situ. Theinner diameter of the annular body may be in the range of 1-5 mm, forexample, in the range of 1-2 mm, in the range of 2-3 mm, in the range of3-4 mm, in the range of 4-5 mm, or in the range of 5-6 mm. For example,in one embodiment, the diameter of the opening is in the range of3.0-4.0 mm, for example, 3.5 mm. In the longitudinal or axial direction,the annular body comprises a cylindrical body having a height, theheight being defined by the spacing between the upper and lower flangescreated when the device is deployed, for example as denoted 304 in FIG.3D. The height should be about equal to the combined thickness of theblood vessel walls which will be joined to form the fistula, forexample, the artery wall and the vein wall in an AVF. For example, theheight may be in the range of 0.25-1.0 mm, for example, in the range of0.25 to 0.5 mm, in the range of 0.5 to 0.7 mm, or in the range of 0.5 to1.0 mm.

The sutureless anastomosis device comprises two sets of what will betermed “deployable hands.” These structures are termed “hands” toemphasize their function of clasping the vessel walls together withoutpuncturing the walls. Each set of deployable hands comprises two or moresubstantially flat or gently curved projections which extend radiallyfrom the annular body, when in the deployed configuration. Thedeployable hands may comprise loops, for example, substantially U-shapedloops, V-shaped loops, or semi-circular loops. Each set of deployablehands may comprise any number, for example, from two to sixteen hands,for example, two, three, four, five, six, seven, eight, nine, or ten ortwelve hands. With the aid of a crossing device, described below, eachset of hands can be delivered to the site of the AVF in a first, stowedposition, i.e. in a configuration wherein the hands are orientedsubstantially parallel to the axial axis of the implant. The hands canbe deployed, for example, by releasing them from the constraints of thedeployment instrument, such that they assume a relaxed positionextending radially from the annular body (FIG. 3D). In oneimplementation, the hands, in the deployed position, extendsubstantially at 90 degrees from the body, i.e. perpendicular to theannular body. In other implementations, the hands may project at anangle varying from 45 to 135 degrees from the longitudinal axis of theimplant.

The hands may comprise an elastic or superelastic malleable metal withshape memory, such as nitinol, which can be cut to create hands thatradially project from the annular body (i.e. the “relaxed” or “deployedposition”). Under tension, the hands can be deflected from theirrelaxed, horizontal position to assume a vertical (i.e., parallel to thelongitudinal axis of the implant) stowed, tensioned configuration, forexample when contained under pressure within a deployment device. Uponbeing released from the constraints of the deployment device, theresilient memory metal comprising each hand flips or folds back to itsrelaxed position, such that the hands in each row are projectingradially from the annular body, collectively forming a flange. Thelength of the hands may be, for example, in the range of 0.5-2.0 mm, forexample, in the range of 0.25 to 0.5 mm, in the range of 0.5 to 0.75 mm,in the range of 0.75 to 1 mm, in the range of 1.0 to 1.25 mm, in therange of 1.25 to 1.5 mm, in the range of 1.5 to 1.75 mm, or in the rangeof 1.75 to 2.0 mm.

The first set of deployable hands is located at the distal end of theannular body (FIG. 3D). The first set of hands may be deployedindependently of the second set of hands. The second set of deployablehands is located at the proximal end of the annular body. The second setof hands may be deployed independently of the first set of hands.

The sutureless anastomosis device will be attached or integrated withthe conduit portion of the implant. The sutureless anastomosis devicewill encircle the distal end of the lumen of the tubular conduit, suchthat fluid flow through the central aperture of the annular element willproceed into the conduit. In another embodiment, the suturelessanastomosis device and the scaffolding of the conduit are formed from asingle piece of material, e.g. a metal tube, for example, a metal tubelaser cut to create the wire elements of the scaffolding and suturelessanastomosis device. In one embodiment, the sutureless anastomosis deviceis manufactured separately from the conduit and is joined thereto by oneor more connecters that attach it to the conduit portion of the implant.The connectors may comprise hooks, barbs, fabric, textile or loops thatconnect to the scaffolding portion of the conduit element, which pierceor extend into the conduit material, or which otherwise hold thesutureless anastomosis device and conduit together.

The sutureless anastomosis device may comprise any suturelessanastomosis device known in the art. For example, the suturelessanastomosis element may comprise devices, or variants thereof, describedin: U.S. Pat. No. 6,152,937, entitled “Medical Graft Connector andMethod of Making and Installing Same,” by Peterson; U.S. Pat. No.5,916,226, entitled “Apparatus and method for improved suturelessanastomosis,” by Tozzi; U.S. Pat. No. 6,440,143, entitled “MedicalAnastomosis Apparatus,” by Swanson et al.; United States PatentApplication Publication Number 20050049675, entitled “Medical Devicesand Related Methods,” by Wallace; United States Patent ApplicationPublication Number 2012/0123512, entitled “Sutureless VascularAnastomosis Connection,” by Asfora et al. In one embodiment, thesutureless anastomotic device comprises a device such as the SymmetryBypass System Aortic Connector™ (St Jude Medical Inc. St. Paul Minn.).

In a preferred implementation, the sutureless anastomosis device doesnot comprise any barbs, hooks, or other structures that puncture theblood vessel walls. Accordingly, the device enables atraumatic creationof AVFs. In an alternative implementation, the sutureless anastomosisdevice comprises one or more barbs, hooks, or like structures thatperforate the target blood vessels to aid in securing the device inplace.

In situ, over time AVF lumens tend to become partially occluded byhyperplastic tissue, thrombus or other biological deposits. Accordingly,in some implementations, the annular structure of the anastomosis deviceis expandable. For example, the expandable annular structure maycomprise a plurality of radially expandable wire segments arrangedradially around the circumference of the annular element. The elementsmay comprise, for example, folded wires, struts, U-shaped wire elements,V-shaped wire elements, or elements otherwise configured to expand underradial pressure exerted within the central lumen to increase thediameter of the central lumen. The individually expandable elements,collectively may be forced to unfold, flatten, or otherwise deform suchthat the diameter of the lumen is maintained. Any number of suchelements may be present, for example, 2, 4, 6, 8, 10, 12, or moreexpandable elements. This ability to expand allows the annular elementto be expanded beyond the nominal deployment diameter in order tomaintain a diameter effective for sufficient blood flow from the arteryto the adjoined vein (e.g. 2-5 mm), for example by periodic stretchingwith a catheter (e.g. balloon catheter) or like instrument inserted intothe AVF aperture. Using an expandable annular element, the AVF may bemaintained at an effective diameter for longer periods of time thanstatic AVFs, using a minimally invasive (e.g. percutaneous) ultrasoundguided procedure to expand the ring.

Crossing Device.

The implant of the invention may be placed in situ to create a fistulaby the use of a crossing device. The crossing device may comprise asingle device or combination of devices which allows for the positioningand placement of the implant to create the fistula, e.g., an AVF.

A first element of the crossing system is the implant housing. Theimplant housing is an assembly at the distal end of the crossing device.The implant housing comprises a device in which the implant can bestowed, delivered to the site of the fistula to be formed, and deployedto form the fistula. The housing is configured to position and releasethe implant in a controlled manner to create the fistula.

At the proximal end of the crossing device is an assembly called thecontrol assembly. The control assembly comprises various controlstructures, which may be actuated to operate the elements of the distalimplant housing assembly. The proximal control assembly is configured tobe ex-vivo, outside the body and to be operated by one or more persons.

Connecting the proximal control assembly and the distal implant housingassembly is an intermediate section comprising a catheter, which housesthe wires or other structures which control the elements distal implanthousing.

The implant housing assembly is compact and generally cylindrical,configured for movement through a blood vessel to its target position.In general, the distal implant housing assembly will have a diameter inthe range of 70-150% of the inner diameter of the blood vessel throughwhich it will be deployed. For example, a diameter in the range of70-90% of the diameter of the vessel is preferred for easy travelthrough the vessel, however, larger diameters may be used in which thevessel is distended by the housing. For placement in the cubital artery,for example, in an average-sized adult, the diameter of the housing willbe in the range of 1.3-2.3 mm (4-7 french). The implant housing may becoated with a low friction polymer, such as silicone or PTFE, to easethe movement of the implant housing through tortuous vessels.

A first function of the implant housing is stowage of the implant andenabling its controlled release to form the fistula when positioned atthe target site. In one embodiment. implant housing comprises an outercovering and an inner core. The implant is stowed in a compressedconformation, within the annular space between the outer housing and theinner core. In the compressed conformation, the first and second set ofhands are deflected so as to be substantially parallel with thelongitudinal axis of the crossing device. At the distal end of the outerhousing, the annular space created between the inner core and outerhousing is open, or may be selectively opened by the operator by the useof actuators controlled at the proximal end. This opening will bereferred to herein as the “implant exit.”

Continuous with the inner core, and extending beyond the distal end ofthe outer housing is the distal tip. The distal tip of the implanthousing comprises a rounded or tapered tip which facilitates themovement of the implant housing through the blood vessels to the targetsite.

The distal tip of the crossing device will comprise one or more markingswhich aid in visualization of the distal implant housing assembly forits guided movement through the blood vessels and its placement at thetarget site. In one embodiment, the one or more markings compriseechogenic markings which are visible using imaging modalities such asultrasound. Such markings may be made of thermoplastic material or metal(e.g., stainless steel) or may comprise of a surface that has beenetched, dimpled or roughened in a manner to enhance detection byultrasound equipment. In one embodiment, the markings compriseradio-opaque markings, comprising gold, platinum, or other radiopaquematerials that can be readily imaged by a radiographic imaging modality,e.g. fluoroscopy. One or more markings may be present on the implant aswell, or the implant may comprise a material that is capable of beingimaged using an external imaging modality.

In one embodiment, the crossing device comprises one or more magneticelements at the distal tip. The magnetic element may be used in thoseimplementations of the system that employ complementary catheters forprecise placement of the distal implant housing assembly at the targetsite, as described below.

In one implementation, the implant housing comprises one or moredeployable cutting elements for piercing the walls of the vessels to bejoined. For example, in one embodiment, the distal tip forms a housingin which a retractable cutting element is housed, which such cuttingelement can be advanced axially from the distal tip in order to pierce,cut, or otherwise create an aperture in the vein wall and to furthercreate an aperture in the adjoining artery to which the vein will beconnected. The cutting element may be extended and retracted by themeans of an actuator, the actuator being in connection with a controlelement in the control assembly at the proximal end of the device. Thecutting element may comprise a needle, blade, or other cuttinginstrument. In one embodiment, the cutting element is a needle wire,i.e. a wire with a needle tip.

The implant housing contains one or more actuators. The one or moreactuators can be engaged, by controls at the proximal end of the device,to advance the implant in the distal direction. The actuators maycomprise any structure or device which controllably advances the implanttowards the implant exit. In one embodiment, the actuator is a pistonconnected to a cable that extends to a control element at the proximalend of the device, such that movement of the control element directlyactuates the piston, which pushes on the implant in the distaldirection. For example, in one embodiment, the the piston comprises aring that fits within the annular space between the outer housing andthe core. In another embodiment, the actuator is a spring-loaded orotherwise tensioned actuator that can be released by means of a latch inconnection with a cable that connects the latch to a control element atthe proximal end, such that the operator can release the spring loadedactuator, which will advance the implant from the implant exit by afixed distance. In another embodiment, the actuator is a motorizeddevice that will advance the implant from the implant exit by a fixeddistance (e.g. stepper motor) or by a distance controlled by theoperator at the proximal end.

The various elements of the distal implant housing assembly, forexample, the actuators that deploy the implant, or actuator that deploythe cutting element, if present, will be responsive to the controlstructures at the proximal control housing. The proximal control housingis configured to remain ex-vivo, outside the patient, where it isaccessible to an operator. The control assembly will comprise controls,for example, knobs, screws, gears, ratchets, plungers, and othermechanical controls, or electronic control elements that can operate theactuators in the distal implant housing assembly.

The proximal control end of the crossing system is in mechanical andcontrol connection with the distal implant housing assembly by acatheter, or like structure, that can be advanced through blood vessels.The catheter will comprise comprising cables, wires, hydraulic channels,moveable rods or other elements for the transmission of mechanicalforces through endoscopic instruments. Alternatively, the controlassembly comprises electronic control elements which are in electricalconnection with powered actuators in the implant housing, such thatsignals transmitted through the catheter can be used to operatemechanical elements in the housing and which can house wires, cables, orother elements connecting the control structures at the proximal endwith actuator elements at the distal end. For example, the catheter maycomprise thermoplastic materials, resins, metal (e.g. stainless steelwire braid) or combinations thereof. The catheter length will be anysufficient to reach the target site from the selected entry point, forexample, in the range of 20-30 cm.

The crossing device may further comprise a guide wire for aiding themovement of the distal implant housing assembly through the blood vesselto the target site. The guide wire may be housed in a channel of theintermediate catheter section, and may be extended from a port presentin the distal implant housing assembly, controlled at the controlassembly by means known in the art. Any vascular guide wire may be used,for example, metal core wires, polymeric wires, and other designs knownin the art, for example, in typical sizes such as 0.46 mm, 0.64 mm, or0.81 mm diameters

In an alternative embodiment, the guide wire is a needle wire, i.e. awire with a needle tip that is deployed to act as both the cuttingelement and the guide wire.

In one implementation, the crossing device is operated in combinationwith a second, complementary placement device. The complementaryplacement device comprises a catheter with a tip, for example, a roundedtip. The tip comprises one or more magnets. The tip may optionallycomprise a hollow channel for receiving the guide wire of the crossingdevice, for example, a central channel with an opening at the distal endof the placement device, extending for a portion of the distal end ofthe placement device.

In this implementation, the implant housing assembly comprises one ormore magnets at the distal tip. The complementary placement devicecomprises a catheter with a distal tip also comprising one or moremagnets. The one or more magnets of the crossing device tip and theplacement device tip may comprise neodymium magnets or other type ofmagnet known in the art. In one embodiment, the magnetic element is anelectromagnet, powered by a power source in the control housing viawires in the catheter. The magnets of the crossing device tip and/orplacement device tip may comprise a ring or doughnut shaped magnet thatdefine or circumscribe the end face of the device, the center portionbeing hollow for the advancement of the implant through the end of thecrossing device and for receiving the cutting element and guide wire inthe case of the placement device. In the implementation of the inventionutilizing magnet-assisted placement, the implant housing assembly of thecrossing device is advanced to the target site in a first blood vesseland the placement device tip is advanced to the target site in a secondblood vessel, wherein, when in sufficient proximity, the magnets will beof sufficient force to attract each other and push the walls of the twovessels together between the two magnetized tips. This enables preciselytargeted deployment of the cutting element to pierce both vessels. Inone embodiment, magnets are present on both the implant housing and thetip of the placement device. In another embodiment, one of the implanthousing or tip of the placement device comprises a magnet while theother comprises one or more ferromagnetic metal elements that attractedto the magnet(s) on the complementary device.

The implant housing may be coated with a low friction polymer, such assilicone or PTFE, to ease the movement of the implant housing throughtortuous vessels.

Methods of Use.

The scope of the invention further encompasses methods of using thedevices described herein to create fistulas, e.g., AVFs. In a generalmethod, the scope of the invention encompasses a method as follows:

a method of forming a fistula comprising a connection between a firstand a second blood vessel in a subject, comprising the following steps:

-   -   an access is created at a selected entry site of the subject;    -   the crossing device is introduced into the vascular system of        the subject via the access;    -   the implant housing is advanced through the vascular system to        the target site, the target site being a site in the first blood        vessel which is in proximity to the second blood vessel;    -   a puncture is made in the first blood vessel and the second        blood vessel;    -   the implant of the invention is advanced such that the hands of        the sutureless anastomosis device are deployed to create a first        and a second flange, in a manner that sandwiches the walls of        the first blood vessel and the second blood vessel between the        first and second flanges and such that such that the lumen of        the annular structure of the implant creates a channel for the        flow of blood between the first and the second blood vessels;    -   the implant housing is withdrawn from the target site, such that        the conduit portion of the implant is deployed in the first        blood vessel proximal to the sutureless anastomosis device;    -   the implant housing is withdrawn from the subject at the access        site.

The general method may be implemented in various ways to achieveselected results, with hardware configured appropriately for performingthe selected method. The method is applied to a subject. The subject maybe any animal, for example a human patient, a test animal, or aveterinary subject. The animal may be in need of treatment for acondition, in need of a fistula, or otherwise selected. In oneembodiment, the subject is a human subject in need of hemodialysistreatment. In one embodiment, the subject is a human in need oftreatment for end-stage renal disease.

The type of fistula to be created will depend upon the needs of thesubject. In one embodiment, the subject is in need of an arteriovenousfistula. In one embodiment, the subject is in need of a venous-venousfistula, for example in a subject in need of treatment for portal venoushypertension.

The entry site will be a site selected based upon its accessibility andits proximity to the target site. For example, in one embodiment, thetarget site is the cephalic vein or the basilica vein in the upper armbetween the shoulder and the elbow, for example as denoted 101 in FIG.1A. An access at this introduction site may be created by any meansknown in the art, for example, by a needle. In one embodiment, access iscreated by the use of a hemostatic valve, also known as an introducersheath. For example, the introducer sheath may comprise a needle,dilator, and sheath portion, wherein the needle is used to first piercethe blood vessel, the dilator is used to widen the opening created bythe needle, and a sheath is introduced to hold the access tract open andto protect the vessel from trauma as the crossing device is introduced,used, and withdrawn. The implant housing of the crossing device isintroduced through the sheath into the tract.

The advancement of the implant housing through the vasculature to thetarget site may be achieved as known in the art, for example, by the useof a conjoined guide wire and/or guided by visualization of thevasculature and the one or more markings of the crossing device, e.g.,echogenic markings visualized by ultrasound or radiopaque markingvisualized by fluoroscope, etc. The advancement of the implant housingmay be achieved by the Seldinger technique, as known in the art. In oneembodiment, the introduction site is the cephalic vein or the basilicavein in the upper arm and the implant housing is advanced in theefferent direction until it reaches the target site.

The location of the target site will depend upon the type of fistula tobe created. In one embodiment, the fistula is an arteriovenous fistula,the first blood vessel is the median cubital perforator, connecting toeither the medial cubital vein, cephalic vein or basilic vein of thearm. The second blood vessel is the brachial artery at its terminus orthe proximal radial or proximal ulnar arteries. Alternative targetsinclude any location that has a perforator branch connecting thesuperficial venous system to the deep venous system, including those ofthe upper arm basilic or forearm basilic or forearm cephalic systems.Other alternatives include perforator connections between superficialand deep systems in the lower leg, as found in the saphenous system.

In one implementation of the invention, the placement of the implanthousing at the target site is achieved by the use of a complementarymagnetic placement device. The placement device is introduced at anaccess site in the second blood vessel, for example, by way of anintroducer sheath. The second access site will be a site in proximity tothe skin and accessible to the target site of the second blood vessel,for example, the radial artery or ulnar artery of the lower arm belowthe elbow, as denoted 104 and 105 in FIG. 1A. The distal tip of theplacement device is then advanced to the target site of the second bloodvessel, for example, by aid of a guide wire and imaging of one or moremarkings on the distal tip of the placement device. When the implanthousing is present at the target site of the first blood vessel and thedistal tip of the placement device is present at the target site of thesecond blood vessel, the attractive forces of the complementary magneticelements of the two devices will create a pinching force to hold thefirst and second blood vessels in alignment.

In those implementations of the invention wherein the complementaryplacement device comprises a hollow chamber, the complementary magneticelements of the crossing device and the complementary placement devicemay be configured such that the cutting element of the crossing deviceand/or the guide wire of the crossing device will be received by thehollow chamber of the placement device, for example, as depicted in FIG.2A-2I.

In an alternative embodiment, only the crossing device is utilized andthe implant housing is aligned at the target site without the aid of aplacement device or magnetic elements.

In one embodiment, the fistula is an AVF fistula, the first blood vesselis the median cubital perforator, and the second blood vessel is thebrachial artery, for example, wherein the target site of the secondblood vessel is the region of the brachial artery just the branching ofthe brachial artery into the ulnar and radial arteries. In alternativeimplementations, either the ulnar or radial artery may serve as thesecond blood vessel, with the target site being a position in the ulnaror radial artery below the terminal branch of the brachial artery,typically in proximity to the cubital fossa.

In most implementations of the invention, upon placement of the implanthousing at the target site (optionally aided by the complementaryplacement device), the one or more cutting elements is deployed,creating a puncture of the first blood vessel and the second bloodvessel. In one embodiment, a guide wire is extended from the implanthousing in first blood vessel into the second blood vessel, followed byintroduction of the distal tip of the implant housing across thepunctured wall of the first blood vessel a short distance into the lumenof the second blood vessel, for example, 1-5 mm, such that the implantexit is present within the second blood vessel. Intraluminal position ofthe implant housing may be confirmed by the return of arterial bloodthrough the proximal end of the crossing device, as visualized byultrasound or fluorscopy and/or needle tip position may be confirmedwith ultrasound.

Following crossing of the distal tip of the implant housing across thepuncture to the second blood vessel, the implant may be deployed. Thedeployment of the implant comprises the following process:

-   -   first, by means of the control elements in the control housing,        an actuator in the implant housing is activated such that the        distal end of the implant is advanced a first distance from the        implant housing exit; wherein the first set of hands is        deployed, wherein upon release of the hands from their deformed,        tensioned position in the implant housing, the hands will        spontaneously revert to their deployed, unconstrained position        substantially perpendicular to the long axis of the implant (for        example, as depicted in FIG. 2F);    -   second, the implant housing is slightly withdrawn such that the        flange formed by the first set of deployed hands is pulled back        against the second blood vessel wall, pressing it against the        neighboring first blood vessel wall, and such that the implant        exit of the second flange is just within the first blood vessel        (for example, as depicted in FIG. 2G);    -   third, by means of the control elements at in the control        housing, the actuator in the implant housing is activated such        that the distal end of the implant is further advanced to a        second distance from the implant housing exit; wherein the        second set of hands is deployed, wherein the release of the        second set of hands from their deformed, tensioned position in        the implant housing results in their spontaneous unfolding to        the unconstrained position substantially perpendicular to the        long axis of the implant (for example, as depicted in FIG. 2H);        and    -   fourth, the implant housing is withdrawn from the target site        such that the conduit section of the implant, held in place by        the deployed flanges, fully withdraws from the implant exit (for        example, as depicted in FIG. 2I), leaving the implant and a        fistula formed thereby in place.

The result of the method is the formation of a fistula, such as an AVF,in a short time by a non-surgical procedure. The fistulas of theinvention, being formed by a non-surgical procedure and by the novel useof a sutureless anastomosis device, may be provided with minimal trauma,greatly reducing inflammation, complications, and the frequency offollow-up intervention.

Following AVF formation, an appropriate entry site may be selected forfor dialysis access, sufficiently superficial to the skin to allow forrepeated venipuncture (within 2 cm). For example, the brachial vein ofthe upper arm or radial or ulnar arteries of the lower arm below theelbow.

Modifications of the above-described process are within the scope of theinvention, and, likewise, the implant and crossing devices may beimplemented by various alternative configurations. For example, in analternative embodiment, the cutting elements are present on thecomplementary placement device. [

Exemplary Embodiments

The foregoing description will enable one of skill in the art toimplement fistulas at various sites in the body, using devices andmethods that embody the several inventive concepts described herein.Following is a roll of exemplary implementations of the devices andmethods.

The scope of the invention encompasses an implant for the creation of afistula between a first and a second blood vessel, the implant having alongitudinal axis from distal to a proximal end, the device comprising:

-   -   a sutureless anastomosis device comprising a first, of hands and        a second set of hands;    -   wherein each hand comprises a body extending at an angle from        the longitudinal axis of the implant;    -   wherein each hand comprises a resilient material such that the        hand may be deflected under tension to a compact orientation        substantially parallel to the longitudinal axis of the implant;    -   wherein each of the first set of hands and the second set of        hands is connected to and arranged around an annular structure        such that the first set of hands forms a first flange and the        second set of hand forms a second flange, wherein the flanges        are separated by a space along the longitudinal axis of the        implant;    -   wherein the device further comprises a conduit comprising a        tubular structure comprising a lumen, connected at its distal        end circumferentially around the proximal end of the annular        structure, wherein the conduit comprises a scaffolding material        enclosed in or surrounded by a covering of biocompatible        material.

In one embodiment, the sutureless anastomosis device comprises 4-12hands. In one embodiment, the hands are substantially perpendicular tothe longitudinal axis of the device. In one embodiment, the handscomprise a material selected from the group consisting of nitinol,stainless steel, and cobalt-chrome. In one embodiment, the handscomprise loops of wire. In one embodiment, the annular structurecomprises an expandable structure. In one embodiment, the conduit istapered, being widest at its proximal end and narrowest at its distalend where it connects to the annular structure. In one embodiment, thecovering of the conduit comprises PTFE film.

In one implementation, the invention encompasses a method of creating anAVF by the implant device above. In a related implementation, the scopeof the invention encompasses the implant described above, for use in thecreation of a fistula between a first and a second blood vessel, whereinblood will flow from the second vessel through the annular structure ofthe sutureless anastomosis device and into the first vessel via thelumen of the conduit. In one embodiment, the fistula is an arteriovenousfistula. In one embodiment, the first blood vessel is the median cubitalperforator, connecting to either the medial cubital vein, cephalic veinor basilic vein of the arm and the second blood vessel is the brachialartery at its terminus or the proximal radial or proximal ulnar artery.In one embodiment, the arteriovenous fistula is created in a subject inneed of dialysis treatment. In one embodiment, the conduit of theimplant is deployed such blood flowing from the second blood vesselthrough the conduit bypasses the deep venous system and flows into thesuperficial venous system.

In one implementation, the scope of the invention encompasses a crossingdevice for deploying the implant described above, comprising

-   -   a catheter comprising proximal end comprising a control assembly        and a distal end comprising an implant housing;    -   wherein the implant housing comprises a deployable cutting        element, a deployable guide wire; a space for storing the        fistula device of any of claims 1-9 such that the hands are in        the compact position; an opening for the implant to exit the        implant housing; and a means of controllably and incrementally        advancing the implant from the opening;    -   wherein the deployable cutting element, the deployable guide        wire; and the means for controllably and incrementally advancing        the implant from the opening are controlled by means of control        elements in the control housing.        In one embodiment, the implant housing comprises one or more        echogenic and/or radiopaque markings for visualization of the        device when deployed in the body of a subject. In one        embodiment, the implant housing comprises one or more magnetic        elements.

The scope of the invention further encompasses a method of forming afistula in a subject wherein the fistula comprises a connection betweena first and a second blood vessel in a subject, comprising the steps:

-   -   creating an access at a selected entry site of the subject;    -   introducing a crossing device into the vascular system of the        subject via the access, wherein the crossing device comprises an        implant housing which houses an implant, wherein the implant may        be controllably deployed from the implant housing; wherein the        implant comprises a sutureless anastomosis device comprising an        annular structure comprising a first set of hands and a second        set of hands wherein the each of the first set of hands and        second set of hands are circumferentially arranged around the        outer diameter of the annular structure; wherein the each set of        hands may be separately released from the implant housing;        wherein upon release from the implant housing, each set of hands        spontaneously assumes a configuration which creates a flange;        wherein the implant further comprises a conduit portion        extending from the proximal end of the annular structure;        wherein the implant housing further comprises a deployable        cutting element;    -   advancing the implant housing of the crossing device through the        vascular system to the target site, the target site being a site        in the first blood vessel which is in proximity to the second        blood vessel;    -   deploying the cutting element to create a puncture in the first        blood vessel and the second blood vessel;    -   advancing the implant from the implant housing to create the        first and the second flange in a manner that sandwiches the        walls of the first blood vessel and the second blood vessel        between the first and second flanges and such that such that the        lumen of the annular structure of the implant creates a channel        for the flow of blood between the first and the second blood        vessels;    -   withdrawing the implant housing from the target site, such that        the conduit portion of the implant is deployed in the first        blood vessel.

In one embodiment, the subject is a human subject. In one embodiment,the subject is a human subject in need of hemodialysis. In oneembodiment, the fistula is an arteriovenous fistula. In one embodiment,the fistula is a venous-venous fistula. In one embodiment, the firstblood vessel is the brachial vein, the access site is the cephalic veinor the basilica vein in the upper arm, and the target site is thebrachial vein wherein it is in proximity to the brachial artery, ulnarartery, or radial artery. In one embodiment, the second blood vessel isthe brachial artery, the ulnar artery, or the radial artery. In oneembodiment, the target site is in the proximity to the branching of thebrachial artery into the ulnar and radial arteries. In one embodiment,the implant housing comprises one or more magnetic elements and themethod further encompasses the use of a placement device comprising oneor more magnetic elements at its distal tip, which distal tip isadvanced to the target site in the second blood vessel, such that theproximity of magnetic elements of the implant housing and placementdevice causes the two structures to pinch the first and second bloodvessel walls together.

In one embodiment, the implant of the invention is deployed from thecrossing device by the following process:

-   -   first, by means of the control elements at the proximal control        housing, an actuator in the implant housing is activated such        that the distal end of the implant is advanced a first distance        from the implant housing exit; wherein the first set of hands is        deployed, such that the distal hands of the implant's sutureless        anastomosis device are liberated from their deformed, tensioned        position in the implant housing and can spontaneously revert to        their deployed, unconstrained position substantially        perpendicular to the long axis of the implant;    -   second, the implant housing is slightly withdrawn such that the        flange formed by the first set of deployed hands is pulled back        against the second blood vessel wall, pressing it against the        neighboring first blood vessel wall, and such that the implant        exit of the second flange is just within the first blood vessel;    -   third, by means of the control elements at the proximal control        housing, the actuator in the implant housing is activated such        that the distal end of the implant is further advanced to a        second distance from the implant housing exit; wherein the        second set of hands is deployed, such that the proximal hands of        the implant's sutureless anastomosis device are liberated from        their deformed, tensioned position in the implant housing and        can spontaneously revert to a deployed, unconstrained position        substantially perpendicular to the long axis of the implant; and    -   fourth, the implant housing is withdrawn from the target site        such that the conduit section of the implant, held in place by        the deployed flanges, fully withdraws from the implant exit,        leaving the implant in place and a fistula formed thereby.

All patents, patent applications, and publications cited in thisspecification are herein incorporated by reference to the same extent asif each independent patent application, or publication was specificallyand individually indicated to be incorporated by reference. Thedisclosed embodiments are presented for purposes of illustration and notlimitation. While the invention has been described with reference to thedescribed embodiments thereof, it will be appreciated by those of skillin the art that modifications can be made to the structure and elementsof the invention without departing from the spirit and scope of theinvention as a whole.

What is claimed is:
 1. An implant for the creation of a fistula betweena first and a second blood vessel, the implant having a longitudinalaxis from a distal to a proximal end, the implant comprising asutureless anastomosis device comprising a first set of hands and asecond set of hands; wherein each hand comprises a body extending at anangle from the longitudinal axis of the implant; wherein each handcomprises a resilient material such that the hand may be deflected undertension to a compact orientation substantially parallel to thelongitudinal axis of the implant; wherein each of the first set of handsand the second set of hands is connected to and arranged around anannular structure such that the first set of hands forms a first flangeand the second set of hand forms a second flange, wherein the flangesare separated by a space along the longitudinal axis of the implant;wherein the implant further comprises a conduit comprising a tubularstructure comprising a lumen, connected at its distal endcircumferentially around the proximal end of the annular structure,wherein the conduit comprises a scaffolding material enclosed in orsurrounded by a covering of biocompatible material.
 2. The implant ofclaim 1, wherein the sutureless anastomosis device comprises 4-12 hands.3. The implant of claim 1, wherein the hands are substantiallyperpendicular to the longitudinal axis of the implant.
 4. The implant ofclaim 1, wherein the hands comprise a material selected from the groupconsisting of nitinol, stainless steel, and cobalt-chrome.
 5. Theimplant of claim 1, wherein the hands comprise loops of wire.
 6. Theimplant of claim 1, wherein the annular structure comprises a radiallyexpandable structure.
 7. The implant of claim 1, wherein the conduit istapered, being widest at its proximal end and narrowest at its distalend where it connects to the annular structure.
 8. The device of claim1, wherein the covering of the conduit comprises PTFE film. 9.-16.(canceled)
 17. A system for deploying a sutureless anastomosis devicecomprising, a sutureless anastomosis device comprising: first set ofhands and a second set of hands; wherein each hand comprises a bodyextending at an angle from the longitudinal axis of the implant; whereineach hand comprises a resilient material such that the hand may bedeflected under tension to a compact orientation substantially parallelto the longitudinal axis of the implant; wherein each of the first setof hands and the second set of hands is connected to and arranged aroundan annular structure such that the first set of hands forms a firstflange and the second set of hand forms a second flange, wherein theflanges are separated by a space along the longitudinal axis of theimplant; wherein the implant further comprises a conduit comprising atubular structure comprising a lumen, connected at its distal endcircumferentially around the proximal end of the annular structure,wherein the conduit comprises a scaffolding material enclosed in orsurrounded by a covering of biocompatible material; and a cathetercomprising a proximal end, the proximal end comprising a controlassembly and a distal end comprising an implant housing; wherein thesutureless anastomosis device is contained within the implant housingand is configured such that the hands are in the compact position;wherein the implant housing comprises a deployable cutting element, adeployable guide wire; and a means of controllably and incrementallyadvancing the implant from the opening; wherein the deployable cuttingelement, the deployable guide wire; and the means for controllably andincrementally advancing the implant from the opening are controlled bymeans of control elements in the control housing.
 18. The crossingdevice of claim 17, wherein the implant housing comprises one or moreechogenic and/or radiopaque markings at its distal tip for visualizationof the distal tip of the crossing device when deployed in the body of asubject.
 19. The delivery tool of claim 17, wherein the implant housingcomprises one or more magnetic elements.
 20. A method of forming afistula in a subject wherein the fistula comprises a connection betweena first and a second blood vessel in a subject, comprising the steps:creating an access at a selected entry site of the subject; introducinga crossing device into the vascular system of the subject via theaccess, wherein the crossing device comprises an implant housing whichhouses an implant, wherein the implant may be controllably deployed fromthe implant housing; wherein the implant comprises a suturelessanastomosis device comprising an annular structure comprising a firstset of hands and a second set of hands wherein the each of the first setof hands and second set of hands are circumferentially arranged aroundthe outer diameter of the annular structure; wherein the each set ofhands may be separately released from the implant housing; wherein uponrelease from the implant housing, each set of hands spontaneouslyassumes a configuration which creates a flange; wherein the implantfurther comprises a conduit portion extending from the proximal end ofthe annular structure; wherein the implant housing further comprises adeployable cutting element; advancing the implant housing of thecrossing device through the vascular system to the target site, thetarget site being a site in the first blood vessel which is in proximityto the second blood vessel; deploying the cutting element to create apuncture in the first blood vessel and the second blood vessel;advancing the implant from the implant housing to create the first andthe second flange in a manner that sandwiches the walls of the firstblood vessel and the second blood vessel between the first and secondflanges and such that such that the lumen of the annular structure ofthe implant creates a channel for the flow of blood between the firstand the second blood vessels; withdrawing the implant housing from thetarget site, such that the conduit portion of the implant is deployed inthe first blood vessel.
 21. The method of claim 20, wherein the fistulais an arteriovenous fistula.
 22. The method of claim 20, wherein thefirst blood vessel is the median cubital perforator, either the medialcubital vein, cephalic vein or basilic vein of the arm and the secondblood vessel is the brachial artery at its terminus or the proximalradial or proximal ulnar artery.
 23. The method of claim 20, wherein thearteriovenous fistula is created in a subject in need of hemodialysistreatment.
 24. The method of claim 20, wherein the conduit is deployedsuch blood flowing from the conduit bypasses the deep venous system andflows into the superficial venous system.